1. Field of the Invention
The instant disclosure relates to a communication device; and more particularly, to a communication device having a stub antenna.
2. Description of Related Art
With the wireless communication technology continues to improve, nowadays the personal electronic products are typically equipped with antenna structures. However, the electromagnetic waves of the electronic products will interfere with other electronic devices and will damage the user's brain. Thus, how to reduce the electromagnetic interference and SAR (Specific Absorption Rate) value of the antenna design is a very important subject.
Currently, SAR value of the standard of the Federal Communications Commission (FCC) specification must be less than 1.6 W/Kg. The user's health is the most important thing, so a good electronic product must have low SAR value for its antenna design to gain acceptance by a country's commercial market.
In addition, FIG. 5 shows one type of the conventional antenna structure 1a. The conventional antenna structure 1a is a feeding antenna used for feeding the signal, which has a feeding portion 11a and a grounding portion 12a. 
When the conventional antenna structure 1a is put in use, it will form a single hotspot 13a, and the measured data of the conventional antenna structure 1a is shown in the table below.
1850 MHzE55.75 V/mSAR1.63 mW/g
The measured data shows the SAR value of the conventional antenna structure 1a can't meet the current international standard. Thus, how to further reduce SAR value of the antenna structure to let the user operates the antenna structure in a more secured environment has become an important issue.